Structure and method for producing multiple size interconnections

ABSTRACT

An electrical structure and method comprising a first substrate electrically and mechanically connected to a second substrate. The first substrate comprises a first electrically conductive pad and a second electrically conductive pad. The second substrate comprises a third electrically conductive pad, a fourth electrically conductive pad, and a first electrically conductive member. The fourth electrically conductive pad comprises a height that is different than a height of the first electrically conductive member. The electrically conductive member is electrically and mechanically connected to the fourth electrically conductive pad. A first solder ball connects the first electrically conductive pad to the third electrically conductive pad. The first solder ball comprises a first diameter. A second solder ball connects the second electrically conductive pad to the first electrically conductive member. The second solder ball comprises a second diameter. The first diameter is greater than said second diameter.

This application is a Continuation of Ser. No. 11/160,669, filed Jul.5,2005.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an electrical structure for producingmultiple size interconnections between substrates.

2. Related Art

Joining substrates together in electrical applications typicallyrequires a large number of connections between the substrates. Thesubstrates may not be large enough to accommodate the large number ofconnections. Therefore there exists a need to accommodate the largenumber of connections necessary to join substrates together inelectrical applications.

SUMMARY OF THE INVENTION

The present invention provides an electrical structure, comprising:

a first substrate comprising a first electrically conductive pad and asecond electrically conductive pad;

a second substrate comprising a third electrically conductive pad, afourth electrically conductive pad, and a first electrically conductivemember, wherein said electrically conductive member is electrically andmechanically connected to said fourth electrically conductive pad,wherein said fourth electrically conductive pad comprises a firstheight, wherein said first electrically conductive member comprises asecond height, and wherein said first height comprises a differentheight than the second height;

a first solder ball electrically and mechanically connecting said firstelectrically conductive pad to said third electrically conductive pad,wherein said first solder ball comprises a first diameter; and

a second solder ball electrically and mechanically connecting saidsecond electrically conductive pad to said first electrically conductivemember, wherein said second solder ball comprises a second diameter, andwherein said first diameter is greater than said second diameter.

The present invention provides an electrical structure, comprising:

a first substrate comprising a first electrically conductive pad and asecond electrically conductive pad;

a second substrate comprising a first layer and a second layer, whereinsaid first layer comprises a third electrically conductive pad, whereinsaid second layer comprises a fourth electrically conductive pad;

a first solder ball electrically and mechanically connecting said firstelectrically conductive pad to said third electrically conductive pad,wherein said first solder ball comprises a first diameter; and

a second solder ball electrically and mechanically connecting saidsecond electrically conductive pad to said fourth electricallyconductive pad, wherein said second solder ball comprises a seconddiameter, wherein said first diameter is greater than said seconddiameter, and wherein a first distance between said first substrate andsaid first layer is greater than a second distance between said firstsubstrate and said second layer.

The present invention provides a method for forming an electricalstructure, comprising:

providing a first substrate comprising a first electrically conductivepad and a second electrically conductive pad;

providing a second substrate comprising a third electrically conductivepad, a fourth electrically conductive pad, and a first electricallyconductive member, wherein said electrically conductive member iselectrically and mechanically connected to said fourth electricallyconductive pad, wherein said fourth electrically conductive padcomprises a first height, wherein said first electrically conductivemember comprises a second height, and wherein said first heightcomprises a different height than said second height;

forming a first solder ball electrically and mechanically connectingsaid first electrically conductive pad to said third electricallyconductive pad, wherein said first solder ball comprises a firstdiameter; and

forming a second solder ball electrically and mechanically connectingsaid second electrically conductive pad to said first electricallyconductive member, wherein said second solder ball comprises a seconddiameter, and wherein said first diameter is greater than said seconddiameter.

The present invention advantageously provides a structure and associatedmethod to accommodate the large number of connections necessary to joinsubstrates together in electrical applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of an electrical structure 2having a substrate electrically and mechanically connected to asubstrate using a plurality of different sized controlled collapse chipconnection (C4) solder balls, in accordance with embodiments of thepresent invention

FIG. 2 illustrates a cross-sectional view of an electrical structurehaving a substrate electrically and mechanically connected to asubstrate comprising a plurality of layers using a plurality ofdifferent sized controlled collapse chip connection (C4) solder balls,in accordance with embodiments of the present invention

FIG. 3 illustrates a top view of the electrical structure of FIG. 1comprising a plurality of C4 solder balls and a plurality of C4 solderballs, in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a cross-sectional view of an electrical structure 2having a substrate 4 electrically and mechanically connected to asubstrate 12 using a plurality of different sized controlled collapsechip connection (C4) solder balls 8, 9, and 11, in accordance withembodiments of the present invention. Alternatively, the C4 solder balls8, 9, and 11 may comprise any type of electrical interconnection forelectrically and mechanically connecting a substrate 4 to a substrate12. Note that the C4 solder balls 8, 9, and 11 are shown forillustration purposes and that an unlimited number of C4 solder ballssimilar to the C4 solder balls 8, 9, and 11 (or any type ofinterconnections) may be used to electrically and mechanically connectto the substrate 4 to the substrate 12. The C4 solder balls 8, 9, and 11each comprise a different size (i.e., a different diameter). Thedifferent sized C4 solder balls 8, 9, and 11 are used to carry differenttypes of signals between the substrate 4 and the substrate 12. Forexample, the largest C4 solder ball 8 may be used to carry a globalpower signal between the substrate 4 and the substrate 12, the nextlargest C4 solder ball 9 may be used to carry a local power signalbetween the substrate 4 and the substrate 12, and the smallest C4 solderball 11 may be used to carry an input/output (I/O) signal between thesubstrate 4 and the substrate 12. A global power signal comprises a highpower signal (e.g., high current in a range of about 100 mA to about 300mA) used to power a plurality of devices on the substrate 4 and/or thesubstrate 12. A local power signal comprises a power signal (e.g.,current in a range of less than about 100 mA) used to power one deviceon the substrate 4 or the substrate 12. The electrical structure 2 mayinclude, inter alia, a high performance ball grid array (HyperBGA®)module. The electrical structure 2 comprising large C4 solder balls(e.g., C4 solder balls 8 and 9 for power signals comprising high currentflow) and small C4 solder balls (e.g., C4 solder ball 11 for I/O signalscomprising low current flow) allows for an increase of a packing densityof the C4 solder balls (i.e., can fit more solder balls) within theelectrical structure 2 over using single sized interconnections whilemaintaining current carrying capabilities of the interconnections.Additionally, the C4 solder balls 8 and 9 are placed on the electricallyconductive member 14 and 16 respectively. This enables the C4 solderballs 8, 9, and 11 to each comprise a portion that is coplanar withrespect to each other so that each of the solder balls 8, 9, and 11 maymake contact with contact pads 15A, 15B, and 15C respectively and thesubstrate 4 may be placed about parallel with the substrate 12. Thefirst substrate 4 and the second substrate 12 may include respectively,inter alia, a semiconductor device and a chip carrier, a semiconductordevice and a printed circuit board, a chip carrier and a semiconductordevice, a printed circuit board and a semiconductor device, a chipcarrier and a printed circuit board, a printed circuit board and a chipcarrier, etc. The semiconductor device may include, inter alia, asemiconductor chip. The chip carrier and the printed circuit board mayinclude, inter alia, an organic or ceramic material. The C4 solder balls8, 9, and 11 may comprise, inter alia, a high melt solder (i.e., theliquidus temperature is greater than about 330° C.). Alternatively, theC4 solder balls 8, 9, and 11 may comprise a low melt solder comprising aSn/Pb alloy composition such that the liquidus temperature does notexceed about 260° C. The low melt solder 8 may include, inter alia, thecompositions and melting points shown in Table 1. TABLE 1 SolderCompositions Liquidus Temperature in Alloy Composition (wt %) DegreesCelsius Eutectic Sn/Pb 63Sn/37Pb 183 Sn/Ag/Pb 62Sn/Ag2/Pb36 189 In/SnIn50/Sn50 125 Sn/Ag/Cu Sn95.75/Ag3.5/Cu0.75 221-227 Sn/Cu Sn99.3/Cu0.7227 Sn/Bi Sn99.85/Bi0.15 232 Sn/Ag Sn97.5/Ag2.5 226

Contact pads 15A, 15C, and 15E are electrically and mechanicallyconnected to wires 6A, 6B, and 6C respectively. Contact pads 15B, 15D,and 15F are electrically and mechanically connected to wires 7A, 7B, and7C respectively. Each of the contact pads 15A . . . 15F comprises aheight H1 and a width W1. Each of the contact pads 15A . . . 15F maycomprise a different height H1 and a different width W1. Alternatively,each of the contact pads 15A . . . 15F may comprise a same height H1 anda same width W1. The height H1 may comprise a height selected from arange of less than about 25 um. The width W1 may comprise a widthselected from a range of about 75 um to about 100 um. The C4 solder ball8 electrically and mechanically connects electrically conductive pad 15Aon the substrate 4 to the electrically conductive pad 15B on thesubstrate 12. D1 is the diameter of the C4 solder ball 8. The diameterD1 of the C4 solder ball 8 may comprise a diameter selected from a rangeof about 100 um to about 500 um. An electrically conductive member 14 iselectrically and mechanically connected to the electrically conductivepad 15D on the substrate 12. The C4 solder ball 9 electrically andmechanically connects the electrically conductive pad 15C on thesubstrate 4 to the electrically conductive member 14 and therefore acombination of the C4 solder ball 9 and the electrically conductivemember 14 electrically connects the electrically conductive pad 15C tothe electrically conductive pad 15D. D2 is a diameter of the C4 solderball 9. The diameter of the C4 solder ball 9 may comprise a diameterselected from a range of about 25 um to about 100 um. The electricallyconductive member 14 has a height H2. The height H2 may comprise a sameheight as the height H1. Alternatively, the height H2 may comprise adifferent height as the height H1. The height H2 may comprise a heightselected from a range of about 40 um to about 60 um. The electricallyconductive member 14 has a width W2. The width W2 may comprise a samewidth as the width W1. Alternatively, the width W2 may comprise adifferent width as the width W1. The width W2 may comprise a widthselected from a range of less than about 50 um. An electricallyconductive member 16 is electrically and mechanically connected to anelectrically conductive pad 15F on the substrate 12. The C4 solder ball11 electrically and mechanically connects the electrically conductivepad 15E on the substrate 4 to the electrically conductive member 16 andtherefore a combination of the C4 solder ball 11 and the electricallyconductive member 16 electrically connects the electrically conductivepad 6C to the electrically conductive pad 7C. D3 is a diameter of the C4solder ball 11. The diameter D3 of the C4 solder ball 11 may comprise adiameter selected from a range of about less than 25 um. The diameter D1is greater than the diameter D2 and the diameter D2 is greater that thediameter D3. The electrically conductive member 16 has a height H3. Theheight H3 may comprise a same height as the height H1 and/or H2.Alternatively, the height H3 may comprise a different height as theheight H1 and/or H2. The height H3 may comprise a height selected from arange of about 65 um to about 85 um. The electrically conductive member16 has a width W3. The width W3 may comprise a same width as the widthW1 and/or W2. Alternatively, the width W3 may comprise a different widthas the width W1 and/or W2. The width W3 may comprise a width selectedfrom a range of less than about 25 um.

FIG. 2 illustrates a cross-sectional view of an electrical structure 20having a substrate 22 electrically and mechanically connected to asubstrate 38 comprising a plurality of layers 24, 34, and 36 using aplurality of different sized controlled collapse chip connection (C4)solder balls 28, 30, and 32, in accordance with embodiments of thepresent invention. Alternatively, the C4 solder balls 28, 30, and 32 maycomprise any type of electrical interconnection for electrically andmechanically connecting a substrate 22 to a substrate 38. Note that theC4 solder balls 28, 30, and 32 are shown for illustration purposes andthat an unlimited number of C4 solder balls similar to the C4 solderballs 28, 30, and 32 (or any type of interconnections) may be used toelectrically and mechanically connect to the substrate 22 to thesubstrate 38. The C4 solder balls 28, 30, and 32 each comprise adifferent size (i.e., a different diameter). The substrate 38 compriseslayers 24, 34, and 36. Each of layers 24, 34, and 36 may be used forcarrying different signal types (e.g., layer 24 carries global powersupply signals, layer 34 carries local power supply signals, and layer36 carries I/O signals). The different sized C4 solder balls 28, 30, and32 are used to carry different types of signals between the substrate 22and layers 24, 34, and 36 within the substrate 38. For example, thelargest C4 solder ball 28 may be used to carry a global power signalbetween the substrate 22 and layer 24 within the substrate 24, the nextlargest C4 solder ball 30 may be used to carry a local power signalbetween the substrate 22 and layer 34 within the substrate 38, and thesmallest C4 solder ball 32 may be used to carry an input/output (I/O)signal between the substrate 22 and layer 36 within the substrate 38.The electrical structure 20 may include, inter alia, a high performanceball grid array (HyperBGA®) module. The electrical structure 20comprising large C4 solder balls (e.g., C4 solder balls 8 and 9 forpower signals comprising high current flow) and small C4 solder balls(e.g., C4 solder ball 11 for I/O signals comprising low current flow)allows for an increase of a packing density of the C4 solder balls(i.e., can fit more solder balls) within the electrical structure 20over using single sized interconnections while maintaining currentcarrying capabilities of the interconnections. Additionally, the layers24, 34, and 36 each comprise a different level with respect to eachother so that the C4 solder balls 28, 30, and 32 may be placed such thatthe C4 solder balls 28, 30, and 32 each comprise a portion that iscoplanar with respect to each other so that each of the solder balls 28,30, and 32 may make contact with the substrate 22 and the substrate 22may be placed about parallel with the substrate 38. The first substrate22 and the second substrate 38 may include respectively, inter alia, asemiconductor device and a chip carrier, a semiconductor device and aprinted circuit board, a chip carrier and a semiconductor device, aprinted circuit board and a semiconductor device, a chip carrier and aprinted circuit board, a printed circuit board and a chip carrier, etc.The semiconductor device may include, inter alia, a semiconductor chip.The chip carrier and the printed circuit board may include, inter alia,an organic or ceramic material. The C4 solder balls 28, 30, and 32 maycomprise, inter alia, a high melt solder (i.e., the liquidus temperatureis greater than about 330° C.) a low melt Sn/Pb solder (i.e., liquidustemperature does not exceed about 260° C.) as described with respect tosolder balls 8, 9, and 11 in the description of FIG. 1.

Contact pads 21A, 21C, and 21E are electrically and mechanicallyconnected to wires 26A, 26B, and 26C respectively. Contact pads 21B,21D, and 21F are electrically and mechanically connected to wires 27A,27B, and 27C respectively. Each of the contact pads 21A . . . 21Fcomprises a height H1 and a width W1. Each of the contact pads 21A . . .21F may comprise a different height H1 and a different width W1.Alternatively, each of the contact pads 21A . . . 21F may comprise asame height H1 and a same width W1. The height H1 may comprise a heightselected from a range of less than about 25 um. The width W1 maycomprise a width selected from a range of about 75 um to about 100 um.The C4 solder ball 28 electrically and mechanically connects anelectrically conductive pad 21A on the substrate 22 to an electricallyconductive pad 21B on layer 24 of the substrate 38. D1 is a diameter ofthe C4 solder ball 28. The diameter D1 of the C4 solder ball 28 maycomprise a diameter selected from a range of about 100 um to about 500um. The layer 24 comprises a thickness T1. The C4 solder ball 30electrically and mechanically connects an electrically conductive pad21C on the substrate 22 to an electrically conductive pad 21D on layer34 of the substrate 38. D2 is a diameter of the C4 solder ball 30. Thediameter D2 of the C4 solder ball 30 may comprise a diameter selectedfrom a range of about 25 um to about 100 um. The layer 34 comprises athickness T2. The C4 solder ball 32 electrically and mechanicallyconnects an electrically conductive pad 21E on the substrate 22 to anelectrically conductive pad 21F on layer 36 of the substrate 38. D3 is adiameter of the C4 solder ball 32. The diameter D3 of the C4 solder ball32 may comprise a diameter selected from a range of about less than 25um. The diameter D1 is greater than the diameter D2 and the diameter D2is greater that the diameter D3. The layer 36 comprises a thickness T3.Each of the thicknesses T1, T2, and T3 may comprise a same thickness.Alternatively, each of the thicknesses T1, T2, and T3 may comprise adifferent thickness.

FIG. 3 illustrates a top view of the electrical structure 2 of FIG. 1comprising a plurality of C4 solder balls 8 and a plurality of C4 solderballs 11 and without the C4 solder ball 9, in accordance withembodiments of the present invention. The C4 solder balls 8 comprise apitch PI (i.e., a center to center measurement) between each adjacent C4solder ball 8. The pitch P1 may be selected from a range of about 200 umto about 500 um. The C4 solder balls 11 comprise a pitch P2 (i.e., acenter to center measurement) between each adjacent C4 solder ball 11.The pitch P2 may be selected from a range of about 50 um or less.

While embodiments of the present invention have been described hereinfor purposes of illustration, many modifications and changes will becomeapparent to those skilled in the art. Accordingly, the appended claimsare intended to encompass all such modifications and changes as fallwithin the true spirit and scope of this invention.

1. An electrical structure, comprising: a first substrate comprising afirst electrically conductive pad and a second electrically conductivepad; a second substrate comprising a first independent layer and asecond independent layer, wherein said first independent layer isconfigured to carry a first signal type, wherein said second independentlayer is configured to carry a second signal type, wherein said firstsignal type differs from said second signal type, wherein said firstindependent layer is separate from said second independent layer,wherein said second independent layer is located over a top surface ofsaid first independent layer, wherein said second independent layer isin direct mechanical contact with said top surface of said firstindependent layer, wherein said first independent layer comprises athird electrically conductive pad, wherein said second independent layercomprises a fourth electrically conductive pad; a first solder ballelectrically and mechanically connecting said first electricallyconductive pad to said third electrically conductive pad, wherein saidfirst solder ball comprises a first diameter; and a second solder ballelectrically and mechanically connecting said second electricallyconductive pad to said fourth electrically conductive pad, wherein saidsecond solder ball comprises a second diameter, wherein said firstdiameter is greater than said second diameter, and wherein a firstdistance between said first substrate and said first independent layeris greater than a second distance between said first substrate and saidsecond independent layer.
 2. The electrical structure of claim 1,further comprising a third solder ball, wherein said first substratecomprises a fifth electrically conductive pad wherein said secondsubstrate comprises a third independent layer, wherein said thirdindependent layer comprises a sixth electrically conductive pad, whereinsaid third independent layer is separate from said second independentlayer, wherein said third layer is located over a top surface of saidsecond independent layer, wherein said third independent layer is indirect mechanical contact with said top surface of said secondindependent layer, wherein said third independent layer comprises asixth electrically conductive pad, wherein said third solder ballelectrically and mechanically connects said fifth electricallyconductive pad to said sixth electrically conductive pad, wherein saidthird solder ball comprises a third diameter, wherein said firstdiameter and said second diameter are each greater than said thirddiameter, and wherein a third distance between said first substrate andsaid third independent layer is less than each of said second distanceand said first distance.
 3. The electrical structure of claim 2, whereinsaid third independent layer is configured to carry a third signal type,and wherein said third signal type differs from said first signal typeand said second signal type.
 4. The electrical structure of claim 1,wherein said first electrically conductive pad comprises a first height,wherein said second electrically conductive pad comprises a secondheight, and wherein said first height differs from said second height.5. The electrical structure of claim 4, wherein said third electricallyconductive pad comprises a third height, wherein said fourthelectrically conductive pad comprises a fourth height, wherein saidthird height differs from said fourth height, and wherein said thirdheight and said fourth height differ from said first height and saidsecond height.
 6. The electrical structure of claim 1, wherein saidfirst electrically conductive pad comprises a first width, wherein saidsecond electrically conductive pad comprises a second width, and whereinsaid first width differs from said second width.
 7. The electricalstructure of claim 6, wherein said third electrically conductive padcomprises a third width, wherein said fourth electrically conductive padcomprises a fourth width, wherein said third width differs from saidfourth width, and wherein said third width and said fourth width differfrom said first width and said second width.
 8. The electrical structureof claim 1, wherein said first substrate comprises a semiconductordevice, and wherein said second substrate comprises a chip carrier. 9.The electrical structure of claim 1, wherein said first solder ballcomprises a power signal solder ball for carrying power signals betweensaid first substrate and said second substrate, and wherein said secondsolder ball comprises an input/output (I/O) signal solder ball forcarrying I/O signals between said first substrate and said secondsubstrate.
 10. The electrical structure of claim 1, wherein said firstindependent layer comprises a first thickness, wherein said secondindependent layer comprises a second thickness, and wherein said firstthickness differs from said second thickness.
 11. A method for formingan electrical structure, comprising: providing a first substratecomprising a first electrically conductive pad and a second electricallyconductive pad; providing a second substrate comprising a firstindependent layer and a second independent layer, wherein said firstindependent layer is configured to carry a first signal type, whereinsaid second independent layer is configured to carry a second signaltype, wherein said first signal type differs from said second signaltype, wherein said first independent layer is separate from said secondindependent layer, wherein said second independent layer is located overa top surface of said first independent layer, wherein said secondindependent layer is in direct mechanical contact with said top surfaceof said first independent layer, wherein said first independent layercomprises a third electrically conductive pad, wherein said secondindependent layer comprises a fourth electrically conductive pad;forming a first solder ball electrically and mechanically connectingsaid first electrically conductive pad to said third electricallyconductive pad, wherein said first solder ball comprises a firstdiameter; and forming a second solder ball electrically and mechanicallyconnecting said second electrically conductive pad to said fourthelectrically conductive pad, wherein said second solder ball comprises asecond diameter, wherein said first diameter is greater than said seconddiameter, and wherein a first distance between said first substrate andsaid first independent layer is greater than a second distance betweensaid first substrate and said second independent layer.
 12. The methodof claim 11, wherein said first substrate comprises a fifth electricallyconductive pad wherein said second substrate comprises a thirdindependent layer, wherein said third independent layer comprises asixth electrically conductive pad, wherein said third independent layeris separate from said second independent layer, wherein said third layeris located over a top surface of said second independent layer, whereinsaid third independent layer is in direct mechanical contact with saidtop surface of said second independent layer, wherein said thirdindependent layer comprises a sixth electrically conductive pad, andwherein said method further comprises: forming a third solder ballelectrically and mechanically connecting said fifth electricallyconductive pad to said sixth electrically conductive pad, wherein saidthird solder ball comprises a third diameter, wherein said firstdiameter and said second diameter are each greater than said thirddiameter, and wherein a third distance between said first substrate andsaid third independent layer is less than each of said second distanceand said first distance.
 13. The method of claim 12, wherein said thirdindependent layer is configured to carry a third signal type, andwherein said third signal type differs from said first signal type andsaid second signal type.
 14. The method of claim 11, wherein said firstelectrically conductive pad comprises a first height, wherein saidsecond electrically conductive pad comprises a second height, andwherein said first height differs from said second height.
 15. Themethod of claim 14, wherein said third electrically conductive padcomprises a third height, wherein said fourth electrically conductivepad comprises a fourth height, wherein said third height differs fromsaid fourth height, and wherein said third height and said fourth heightdiffer from said first height and said second height.
 16. The method ofclaim 11, wherein said first electrically conductive pad comprises afirst width, wherein said second electrically conductive pad comprises asecond width, and wherein said first width differs from said secondwidth.
 17. The method of claim 16, wherein said third electricallyconductive pad comprises a third width, wherein said fourth electricallyconductive pad comprises a fourth width, wherein said third widthdiffers from said fourth width, and wherein said third width and saidfourth width differ from said first width and said second width.
 18. Themethod of claim 11, wherein said first substrate comprises asemiconductor device, and wherein said second substrate comprises a chipcarrier.
 19. The method of claim 11, wherein said first solder ballcomprises a power signal solder ball for carrying power signals betweensaid first substrate and said second substrate, and wherein said secondsolder ball comprises an input/output (I/O) signal solder ball forcarrying I/O signals between said first substrate and said secondsubstrate.
 20. The method of claim 11, wherein said first independentlayer comprises a first thickness, wherein said second independent layercomprises a second thickness, and wherein said first thickness differsfrom said second thickness.